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A097982
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Numbers n such that (phi(n) + sigma(n))/(rad(n))^2 is an integer > 1 (phi=A000010, sigma=A000203, rad=A007947).
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3
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864, 2430, 7776, 27000, 55296, 69984, 82134, 215622, 432000, 497664, 629856, 675000, 862488, 1499136, 1749600, 2187000, 2667168, 3449952, 3538944, 4287500, 4312440, 4478976, 4563000, 5668704, 6912000, 10800000, 13045131, 13799808
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| J.-M. De Koninck and A.Mercier, 1001 Problemes en Theorie Classique Des Nombres, Problem 749 pp. 95, 319, Ellipses Paris 2004.
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EXAMPLE
| For example: phi(864) = 288, sigma(864) = 2520, 864 = 2^5*3^3. (288+2520)/6^2 = 78.
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MATHEMATICA
| f[n_] := (DivisorSigma[1, n] + EulerPhi[n])/(Times @@ Transpose[FactorInteger[n]][[1]])^2; Do[ If[IntegerQ[f[n] && f[n] != 1], Print[n]], {n, 2, 1000000}] - Tanya Khovanova (tanyakh(AT)yahoo.com), Aug 30 2006
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CROSSREFS
| Sequence in context: A184451 A203662 A179671 * A064321 A082243 A114497
Adjacent sequences: A097979 A097980 A097981 * A097983 A097984 A097985
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KEYWORD
| nonn
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AUTHOR
| Lekraj Beedassy (blekraj(AT)yahoo.com), Sep 07 2004
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EXTENSIONS
| More terms from Tanya Khovanova (tanyakh(AT)yahoo.com), Aug 30 2006
a(14)-a(28) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Feb 05 2010
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